U.S. patent number 10,591,346 [Application Number 15/741,640] was granted by the patent office on 2020-03-17 for fluid monitoring apparatus including fluid density detection system for subsea apparatus.
This patent grant is currently assigned to EQUINOR ENERGY AS. The grantee listed for this patent is STATOIL PETROLEUM AS. Invention is credited to Idar Olav Grytdal.
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United States Patent |
10,591,346 |
Grytdal |
March 17, 2020 |
Fluid monitoring apparatus including fluid density detection system
for subsea apparatus
Abstract
Subsea equipment-protection apparatus including a fluid
monitoring apparatus for detecting a first fluid, a second fluid
and a third fluid. The fluid monitoring apparatus including a first
float having a density less than that of the first fluid but
greater than that of the second fluid; a second float having a
density less than that of the second fluid but greater than that of
the third fluid; and a sensor configured to detect the first and
second floats so that the position of the floats can be determined.
The first float floating when a fluid with density greater than the
first float is present and sinking when a fluid with density less
than the first float is present. The second float floating when a
fluid with a density greater than the second float is present and
sinking when a fluid with a density less than the second float is
present.
Inventors: |
Grytdal; Idar Olav (Ranheim,
NO) |
Applicant: |
Name |
City |
State |
Country |
Type |
STATOIL PETROLEUM AS |
Stavanger |
N/A |
NO |
|
|
Assignee: |
EQUINOR ENERGY AS (Stavanger,
NO)
|
Family
ID: |
54062701 |
Appl.
No.: |
15/741,640 |
Filed: |
July 8, 2015 |
PCT
Filed: |
July 08, 2015 |
PCT No.: |
PCT/EP2015/065620 |
371(c)(1),(2),(4) Date: |
January 03, 2018 |
PCT
Pub. No.: |
WO2017/005322 |
PCT
Pub. Date: |
January 12, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190113380 A1 |
Apr 18, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01M
3/3245 (20130101); G01N 9/12 (20130101); G01F
23/38 (20130101); G01N 9/18 (20130101); G01F
23/72 (20130101); G01F 23/76 (20130101) |
Current International
Class: |
G01F
23/28 (20060101); G01M 3/32 (20060101); G01F
23/38 (20060101); G01N 9/18 (20060101); G01N
9/12 (20060101); G01F 23/72 (20060101); G01F
23/76 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
International Search Report dated Mar. 31, 2016 in International
Application No. PCT/EP2015/065620. cited by applicant .
Written Opinion of the International Searching Authority dated Mar.
31, 2016 in International Application No. PCT/EP2015/065620. cited
by applicant.
|
Primary Examiner: Patel; Harshad R
Assistant Examiner: Plumb; Nigel H
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. A subsea equipment-protection apparatus comprising a fluid
monitoring apparatus for detecting which of a first fluid, a second
fluid and a third fluid is present, the second fluid having a
density less than the first fluid and the third fluid having a
density less than the second fluid, the fluid monitoring apparatus
comprising: a first float having a density less than that of the
first fluid but greater than that of the second fluid; a second
float having a density less than that of the second fluid but
greater than that of the third fluid; and a sensor, the first float
being allowed to float when a fluid with density greater than the
density of the first float is present and being allowed sink when a
fluid with density less than the density of the first float is
present, the second float being allowed to float when a fluid with
a density greater than the density of the second float is present
and being allowed to sink when a fluid with a density less than the
density of the second float is present, and the sensor being
configured to detect the first float and the second float so that
the position of the floats can be determined.
2. The subsea equipment-protection apparatus as claimed in claim 1,
comprising: a passageway through which fluid may pass from a first
end to a second end, the passageway having a first opening at the
first end and a second opening at the second end, the apparatus
being arranged such that the first float and the second float may
float and sink relative to the passageway in order to open and
close the passageway dependent on the density of fluid present.
3. The subsea equipment-protection apparatus as claimed in claim 2,
the first float being allowed to float to a first position when a
fluid with density greater than the density of the first float is
present and being allowed sink to a second position when a fluid
with density less than the density of the first float is present,
and the second float being allowed to float to a first position
when a fluid with a density greater than the density of the second
float is present and being allowed to sink to a second position
when a fluid with a density less than the density of the second
float is present, the apparatus being configured such that the
second float seals the first opening of the passageway when in the
first position, and the first float and the second float are
distant from the first opening of the passageway when in the second
positions thus allowing fluid to pass through the passageway.
4. The subsea equipment-protection apparatus as claimed in claim 2,
the first float being allowed to float to a first position when a
fluid with density greater than the density of the first float is
present and being allowed sink to a second position when a fluid
with density less than the density of the first float is present,
and the second float being allowed to float to a first position
when a fluid with a density greater than the density of the second
float is present and being allowed to sink to a second position
when a fluid with a density less than the density of the second
float is present, the apparatus being configured such that the
first float seals the second opening of the passageway when in the
second position, and the first float and the second float are
distant from the second opening of the passageway when in the first
positions thus allowing fluid to pass through the passageway.
5. The subsea equipment-protection apparatus as claimed in claim 2,
wherein the first and/or second float comprises a stopping member
configured to prevent the first and/or second float from being
fully withdrawn from the passageway.
6. The subsea equipment-protection apparatus as claimed in claim 5,
wherein the stopping member comprises openings for allowing fluid
to pass therethrough.
7. The subsea equipment-protection apparatus as claimed in claim 1,
wherein the first fluid is sea water, the second fluid is oil and
the third fluid is gas.
8. The subsea equipment-protection apparatus as claimed in claim 1,
wherein the first and second floats are each provided with stops
configured to limit the extent of their relative displacement.
9. The subsea equipment-protection apparatus as claimed in claim 1,
further comprising a protective cap.
10. The subsea equipment-protection as claimed in claim 1,
comprising a surface, the surface comprising an opening in which
the fluid monitoring apparatus is located.
11. The subsea equipment-protection as claimed in claim 10, wherein
the surface is convex, the fluid monitoring apparatus and the
opening being located in an upper portion of the surface.
12. A fluid monitoring apparatus for detecting which of a first
fluid, a second fluid and a third fluid is present, the second
fluid having a density less than the first fluid and the third
fluid having a density less than the second fluid, the apparatus
comprising: a first float having a density less than that of the
first fluid but greater than that of the second fluid; a second
float having a density less than that of the second fluid but
greater than that of the third fluid; a sensor, the first float
being allowed to float when a fluid with density greater than the
density of the first float is present and being allowed sink when a
fluid with density less than the density of the first float is
present, the second float being allowed to float when a fluid with
a density greater than the density of the second float is present
and being allowed to sink when a fluid with a density less than the
density of the second float is present, and the sensor being
configured to detect the first float and the second float so that
the position of the floats can be determined; a passageway through
which fluid may pass from a first end to a second end, the
passageway having a first opening at the first end and a second
opening at the second end, the apparatus being arranged such that
the first float and the second float may float and sink relative to
the passageway in order to open and close the passageway dependent
on the density of fluid present, wherein the first float and the
second float each comprise an end portion and a rod portion, the
rod portions of the first and second floats both passing at least
partially through the passageway, the end portions of the first and
second floats being orientated perpendicularly to the rod portions,
and the end portion of the first and/or second float being shaped
to seal the passageway.
13. The fluid monitoring apparatus as claimed in claim 12, wherein
the rod portions of the first and second float may be configured to
slide relative to one another telescopically.
14. A fluid monitoring apparatus for detecting which of a first
fluid, a second fluid and a third fluid is present, the second
fluid having a density less than the first fluid and the third
fluid having a density less than the second fluid, the fluid
monitoring apparatus comprising: a first float having a density
less than that of the first fluid but greater than that of the
second fluid; a second float having a density less than that of the
second fluid but greater than that of the third fluid; a passageway
through which fluid may pass from a first end to a second end, the
passageway having a first opening at the first end and a second
opening at the second end; and a sensor, the first float being
allowed to float when a fluid with density greater than the density
of the first float is present and being allowed sink when a fluid
with density less than the density of the first float is present,
the second float being allowed to float when a fluid with a density
greater than the density of the second float is present and being
allowed to sink when a fluid with a density less than the density
of the second float is present, the sensor being configured to
detect the first float and the second float so that the position of
the floats can be determined, wherein the first and/or second float
comprises a stopping member configured to prevent the first and/or
second float from being fully withdrawn from the passageway,
wherein the first float and the second float may float and sink
relative to the passageway in order to open and close the
passageway dependent on the density of fluid present, and wherein
the stopping member of the first and/or second float is housed
within a protective cap.
15. A fluid monitoring apparatus for detecting which of a first
fluid, a second fluid and a third fluid is present, the second
fluid having a density less than the first fluid and the third
fluid having a density less than the second fluid, the apparatus
comprising: a first float having a density less than that of the
first fluid but greater than that of the second fluid; a second
float having a density less than that of the second fluid but
greater than that of the third fluid; and a sensor, the first float
being allowed to float when a fluid with density greater than the
density of the first float is present and being allowed sink when a
fluid with density less than the density of the first float is
present, the second float being allowed to float when a fluid with
a density greater than the density of the second float is present
and being allowed to sink when a fluid with a density less than the
density of the second float is present, and the sensor being
configured to detect the first float and the second float so that
the position of the floats can be determined, wherein the sensor
comprises a magnet attached to the first and/or second float and a
coil surrounding the magnet.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to a fluid monitoring apparatus.
It is important in many types of industry, for example in the oil
and gas industry, to be able to monitor what fluids are present in
a system. For example, in the oil and gas industry, in the vicinity
of subsea equipment sea water is typically present. However, during
leaks, hydrocarbons such as oil and gas may leak into the
surrounding environment. It is desirable to detect such leaks.
2. Description of the Related Art
Previous methods of detecting such leaks have included using a
monitoring apparatus that includes electrodes that can detect
whether sea water, oil or gas is present. These have the
disadvantage, however, of gathering salts around the electrodes
that affect their performance and eventually prevent them from
functioning. It is therefore desirable to provide a more reliable
and robust apparatus.
SUMMARY OF THE INVENTION
The present invention provides a fluid monitoring apparatus for
detecting which of a first fluid, a second fluid and a third fluid
is present, the second fluid having a density less than the first
fluid and the third fluid having a density less than the second
fluid, the apparatus comprising: a first float having a density
less than that of the first fluid but greater than that of the
second fluid; a second float having a density less than that of the
second fluid but greater than that of the third fluid; and a
sensor, the first float being allowed to float when a fluid with
density greater than the density of the first float is present and
being allowed sink when a fluid with density less than the density
of the first float is present, the second float being allowed to
float when a fluid with a density greater than the density of the
second float is present and being allowed to sink when a fluid with
a density less than the density of the second float is present, and
the sensor being configured to detect the first float and the
second float so that the position of the floats can be
determined.
Thus, the present invention allows for the detection of different
fluids based upon the location of two floats with different
densities. The use of floats and the physical principals of
buoyancy gives an extremely reliable, robust and accurate
apparatus. The simplicity of the present apparatus, for example in
comparison to the prior electrode detectors, also leads to it being
reliable and robust. The first float may move between a first
position and a second position. In use, the first position of the
first float may be an upper position and the second position may be
a lower position. The second float may also move between a first
position and a second position. These two positions are not
necessarily the same as the two positions of the first float,
indeed preferably they are different positions compared to the two
positions of the first float. In use, the first position of the
second float may be an upper position and the second position may
be a lower position. The first and second positions may be extreme
positions of the floats' displacements, the floats' displacement
being limited by some limiting means.
By floating it may be understood that float is rising with respect
to the remainder of the apparatus. By sinking it may be understood
that the float is lowering with respect to the remainder of the
apparatus.
The sensor may detect motion of the first and/or second float
between the first and second positions, rather than the position of
the floats themselves. Alternatively, or additionally, the position
of the floats may be measured.
By fluid being present, it is meant that there is fluid in the
vicinity of the fluid monitoring apparatus, i.e. fluid immediately
surrounding the floats such that the presence of such a fluid would
cause the floats to react accordingly under the physical laws of
buoyancy.
The first and second position of the first float may be positions
relative to the remainder of the apparatus (i.e. the apparatus
other than the floats), or may be positions relative to the second
float. The first and second position of the second float may be
positions relative to the remainder of the apparatus (i.e. the
apparatus other than the floats), or may be positions relative to
the first float.
The displacement of the first float between the first float's first
and second positions and the displacement of the second float
between the second float's first and second positions may be
different. This may allow the sensor to more easily detect which
float is moving/has moved, for example by detecting the degree of
movement of parts and comparing this to the possible displacement
of the first and second float.
The floats may be formed of plastic, such as high density plastic,
or resin. The floats may be formed of a high density plastic foam.
Foam is particularly useful since the density of the floats can be
very accurately tuned during manufacture, by simply increasing or
decreasing the proportion of pores/air within the foam. During
manufacture the material of the floats is selected and/or modified
such that the density of the first float is between that of the
density of the first and second fluids and the density of the
second float is between that of the density of the second and third
fluids.
The fluid monitoring apparatus may include a passageway through
which fluid may pass from a first end to a second end, the
passageway having a first opening at the first end and a second
opening at the second end, the apparatus being arranged such that
the first float and the second float may float and sink relative to
the passageway in order to open and close the passageway dependent
on the density of fluid present. One or both floats may hence
include a seal for closing the passageway, or may be coupled to
such a seal so that the seal moves when the float moves.
Thus, the fluid monitoring apparatus may act as both a fluid
detector and also as an automatic fluid vent. This can be
advantageous as fluid either above/below a certain threshold
density can be vented to prevent build up of that fluid whilst
fluid below/above that threshold can be contained. In certain
circumstances, certain fluids can be retained as their spread can
be undesirable/dangerous, whilst other certain fluids can be vented
as their build up can be undesirable/dangerous. For instance in the
field of oil and gas, it is desirable to contain an oil leak but to
vent a gas leak.
The prior electrode detectors discussed above do not have such a
passageway. In order to prevent build up of pressure a separate
drill hole needed to be present to allow fluids to vent. The
present invention does not require a separate drill hole to be
present.
The passageway may have a diameter of between 5 mm and 15 mm,
preferably between 6 mm and 10 mm.
In use, the first opening may be a lower opening of the passageway,
and the second opening may an upper opening of the passageway. The
passageway may generally extend vertically. The passageway may be
defined by a sleeve, which may have any cross-section shape, but is
preferably circular.
The fluid monitoring apparatus may be configured such that the
second float seals the first opening of the passageway when in the
first position, and the first float and the second float are
distant from the first opening of the passageway when in the second
positions thus allowing fluid to pass through the passageway.
In this case, when fluid of a density greater than the density of
the first float (i.e. the first fluid) is present, the first and
second floats will both float and may be in their first positions
respectively with the first opening of the passageway sealed by a
seal that is a part of or is connected to the second float. When
fluid of a density less than the density of the first float but
greater than the density of the second float (i.e. the second
fluid) is present, the first float will sink and may be in its
second position and the second float will still float and may be in
its first position, the second float thus still sealing the first
opening. When fluid of a density less than the density of the
second float (i.e. the third fluid) is present, the first and
second floats both sink and may be both in their second positions.
The second float being away from its first position will move the
seal away from the first opening of the passageway opening the
passage way so that fluid can pass through the passageway.
When the first and/or second fluids are present, there is a
positive buoyancy force acting on the second float that presses the
second float upwards against the first opening of the passageway.
This pressing force can add to the sealing effect.
When the first fluid is replaced by the second fluid, the first
float sinks but the second float remains pressed against the first
opening. When the second fluid is replaced by the first fluid then
the first float will float upward.
When the second fluid is replaced by the third fluid, the second
float sinks. This breaks the seal. When the third fluid is replaced
by the second fluid, the second float floats. Once the second float
reaches its first position, the seal may be formed.
When the first fluid is replaced by the third fluid, the first and
second floats sink. This breaks the seal. When the third fluid is
replaced by the first fluid, the first and second floats float.
Once the second float reaches its first position, the seal may be
formed.
This arrangement may be used within an oil and gas installation to
release gas from a cavity in which it might otherwise build up.
Thus, gas may be the third fluid, which is vented, whereas the
second fluid, oil for example, is contained but its presence can be
detected due to movement of the first float.
In alternative arrangement, the fluid monitoring apparatus may be
configured such that the first float seals the second opening of
the passageway when in the second position, and the first float and
the second float are distant from the second opening of the
passageway when in the first positions thus allowing fluid to pass
through the passageway. Thus, the arrangement may effectively be
the inverse of the above described arrangement in relation to the
open and closed state of the passageway and the density of the
fluid.
In this case, when fluid of a density less than the density of the
second float (i.e. the third fluid) is present, the first and
second floats are in their second positions respectively and the
first float seals the second opening of the passageway. When fluid
of a density greater than the density of the second float but less
than the density of the first float (i.e. the second fluid) is
present, the first float is in its second position and the second
float is in its first position, the first float thus sealing the
second opening. When fluid of a density greater than the density of
the first float (i.e. the first fluid) is present, the first and
second floats are in their first positions. The first float being
away from its second position means that the second opening of the
passageway is no longer sealed, and so fluid can pass through the
passageway.
When the second and/or third fluids are present, there is a
negative buoyancy force acting on the first float that presses the
first float downwards against the second opening of the passageway.
This pressing force can add to the sealing effect.
When the third fluid is replaced by the second fluid, the second
float floats but the first float remains pressed against the second
opening. When the second fluid is replaced by the third fluid, the
second float sinks.
When the second fluid is replaced by the first fluid then the first
float floats. This breaks the seal. When the first fluid is
replaced by the second fluid, the first float sinks. Once the first
float reaches its second position, the seal may be formed.
When the third fluid is replaced by the first fluid, the first and
second floats float. This breaks the seal. When the first fluid is
replaced by the third fluid, the first and second floats float.
Once the first float reaches its second position, the seal may be
formed.
The first fluid may be sea water, the second fluid may be oil, e.g.
crude oil, and the third fluid may be gas, e.g. natural gas. The
floats may hence be provided with respective densities that are
between the density of oil and water, for the first float, and
between the density of water and gas, for the second float. The
present invention is particularly advantageous in the field of oil
and gas production. The present invention can detect leaks of both
oil and gas, and can differentiate between the two, in subsea
locations. Further, it is possible for the apparatus to be
installed into a subsea cap or the like. Such a cap may be located
and configured such that rising fluid (e.g. oil/gas) may be trapped
within the cap. This could lead to dangerously large pressures of
gas building up. To avoid this, the venting function of the
invention allows for the gas to vent. Thus, oil and gas leaks can
be detected. The oil can be contained, whilst gas leaks can be
vented.
The fluid monitoring apparatus of the present invention may be
particularly reliable, robust and accurate when the fluids are sea
water, oil and gas. The densities of sea water and oil and gas are
all quite different. The inventors have recognised that using the
principles of buoyancy instead of the prior-known electrode system
provides a much more effective and reliable monitor for sea water,
oil and gas in particular.
Of course, whilst these advantages are particularly apparent in the
field of oil and gas, it should be understood that preventing
building up of certain fluids, whilst containing other fluids, can
be advantageous in other fields as well.
An advantage of one of the example embodiments of the invention is
that it can allow for both the detection of the first and second
fluid replacing the less dense third fluid, and also for the
selective draining of the denser first fluid.
The first float and/or the second float may comprise an end portion
and a rod portion. The rod portions of the first and second floats
may both pass at least partially through the passageway. The/each
end portion may be orientated perpendicularly to the rod portions.
The/each end portion may comprise a planar portion that is
orientated perpendicularly to the axis of the/each rod portion. The
end portion of the first and/or second float may be shaped such
that it may seal the passageway.
The end portion of the second float may be shaped such that it may
seal the second opening of the passageway when in the second
position. The end portion of the first float portion may be shaped
such that it may seal the first opening of the passageway when in
the first position. The/each end portion may be substantially
planar in shape, and the plane may be normal to the rod. The/each
end portion may be disk-shaped.
The end portion of the first float may have a greater
cross-sectional area than the end portion of the second float. This
arrangement may be used when the apparatus is arranged to open a
passageway when the least dense fluid is present.
The end portion of the second float may have a greater
cross-sectional area that the end portion of the first float. This
arrangement may be used when the apparatus is arranged to open a
passageway when the most dense fluid is present.
Whichever float is not performing the sealing function may have a
smaller end portion than the float that is performing the sealing
function. This can help to reduce the size of the apparatus. Only
the end portion of the float that is performing the sealing may be
required to be large enough to seal the passageway.
The first float may comprise a stopping member configured to
prevent the first float from being fully withdrawn from the
passageway. The stopping member may be located at an end of the rod
distant from the end portion of the first float. The stopping
member may be located outside of the passageway. The stopping
member may be shaped such that it may prevent the first float from
being fully withdrawn from the passageway.
Alternatively or additionally, the second float may comprise a
stopping member configured to prevent the second float from being
fully withdrawn from the passageway. The stopping member may be
located at an end of the rod distant from the end portion of the
second float. The stopping member may be located outside of the
passageway. The stopping member may be shaped such that it may
prevent the second float from being fully withdrawn from the
passageway.
Thus, the stopping member can limit the extent to which the first
and/or second floats float and/or sink relative to the passageway,
thus at least partially defining the first and/or second positions.
The limit of the relative displacement of the first/second float
and the passageway may be around 10 cm, 5 cm or 1 cm.
The stopping member may comprise openings to allow fluid to pass
therethrough. Thus, when the apparatus is configured to allow
venting of fluid, the fluid may also freely vent through the
stopping member.
The first and second floats may be configured to slide relative to
one another. The rod portions of the first and second float may be
configured to slide relative to one another telescopically.
In one example embodiment, the rod of the first float may protrude
into the rod of the second float. This is preferably the case when
it is the second float that seals against the first opening of the
passageway. The first float may be nested within the second
float.
In another example embodiment, the rod of the second float may
protrude into the rod of the first float. This is preferably the
case when it is the first float that seals against the second
opening of the passageway. The second float may be nested within
the first float.
The rods may generally be cylindrical in shape.
The floats may be arranged such that the rods and/or end portions
are generally concentric.
In either case, the inner rod may protrude through the end portion
of the outer rod, and then through the rod of the outer rod. There
may be a clearance between the outer diameter of the inner rod and
the diameter of the bore in the outer rod into which the inner rod
is located/nested. Such a clearance may allow for fluid to enter
and to be expelled from the bore as the inner rod exits and enters
the bore respectively. This reduces drag on the relative motion of
the floats. This clearance may be between 1 mm and 10 mm, depending
on the fluid present. For example, when sea water is present, a
clearance of 5 mm may be preferable.
The density of the first float may be only slightly less than the
density of the first fluid, e.g. 15% less, 10% less, 5% less or 1%
less. The density of the second float may be only slightly less
than the density of the second fluid, e.g. 15% less, 10% less, 5%
less or 1% less. The density of the first float may be only
slightly greater than the density of the second fluid, e.g. 15%
more, 10% more, 5% more or 1% more. The density of the second float
may be only slightly greater than the density of the third fluid,
e.g. 15% more, 10% more, 5% more or 1% more.
For example, when the first fluid is sea water (density of
approximately 1000 kg/m.sup.3), the second fluid is (crude) oil
(density of approximately 800 kg/m.sup.3), and the third fluid is
(natural) gas (density of approximately 0.5-10 kg/m.sup.3,
depending on the temperature and pressure), the density of the
first float may be 900 kg/m.sup.3 and the density of the second
float may be 300 kg/m.sup.3.
The first and second floats may be each provided with a stop to
limit the extent of their relative displacement. The stops may be
housed within the telescoping system. The stops may comprise a
groove and peg arrangement between the inner bore of the outer rod
and the inner rod. The limit of their relative displacement may be
around 10 cm, 5 cm or 1 cm. Thus, in use, due to the stops and the
relative buoyancy of the floats, the sinking or floating of the
first/second float may lead to the second/first float falling and
rising with the first/second float accordingly.
When the second fluid is present, the first and second floats may
be configured such that the positive buoyancy force of the second
float may be greater than the negative buoyancy force of the first
float. This means that, in use, when the first float sinks relative
to the second float, the first float can be stopped (in its second
position) and held/supported by the second float.
When the second fluid is present, the first and second floats may
be configured such that the negative buoyancy force of the first
float is greater than the positive buoyancy force of the second
float. This means that, in use, when the second float floats
relative to the first float, the second float can be stopped (in
its first position) and held by the first float.
The fluid monitoring apparatus may further comprise a protective
cap. The protective cap may cover the first opening. The protective
cap may cover the second opening. There may be two protective caps,
one covering each opening. In the case where one protective cap is
present, it may cover the opening distant from the end portions of
the floats, i.e. if the end portions are proximate the first
opening, the end cap may cover the second opening and vice
versa.
The protective cap may comprise openings for allowing fluid to pass
therethrough.
The stopping member of the first and/or second float may be housed
within the protective cap. The end portions of the first and second
floats may be housed within the protective cap. The cap may be
shaped such that it does not limit the movement of the
float(s).
The sensor may comprise a magnet attached to the first and/or
second float and a coil surrounding the magnet. When the floats are
in a telescoping arrangement, the magnet may be attached to the
inner float (only). The magnet may be a permanent magnet. Each
float may comprise a magnet.
The coil may be comprised of a metal, for example copper.
The coil may surround the passageway.
The axis of the coil may extend in the direction of movement of the
floats. Thus, in use, the axis of the coil may be arranged
substantially vertically. The coil and the floats may be
substantially concentrically arranged.
The apparatus may comprise a tube that defines the passageway. The
tube may have any cross section shape, but is preferably annular in
cross section. The coil may also surround the tube. The coil may be
attached to the tube. In use, the axis of the tube may be
substantially vertical.
In use, fluid may pass through the passageway between the inner
wall of the tube and the floats. There may be a gap between the
tube and the floats. The gap may be annular. The gap may be between
the tube and the outer rod of the telescopic floats. There may be
means, e.g. struts or elongated ridges, present in order to
maintain the gap between the tube and the floats.
The coil may be housed within a coil housing, which may be a cast
housing. The coil housing may be comprised of plastic material. The
coil housing may have an annular cross section. In use, the axis of
the coil housing may be substantially vertical. The coil housing
may surround the tube. The coil housing may be attached to the
tube. During manufacture, the coil may be placed around the tube
and plastic may be cast onto the tube, encapsulating the coil and
forming the coil housing.
The coil may be electrically connected to a connector. The
connector may be suitable for connecting a cable to in order to
monitor the sensor. The cable may be suitable for connecting to a
subsea control module. Alternatively, the coil may be configured to
be directly connected to a cable, which may connect to a subsea
control module.
The sensor may use the interaction of the magnet and coil to
determine a movement of the float. Take, for example, the case
where the first float has the magnet attached to it, the first
fluid is present and both the first and second floats are in their
first positions (e.g. adjacent the first, lower opening of the
passageway). When the first fluid is replaced by the second fluid,
the first float may sink and the second float may remain in its
first position. The first float may be stopped in its second
position by its interaction with the second float. The
displacement/motion of the first float may be detected by the
sensor. For example, this may occur as the magnet moves relative to
the coil thereby generating a voltage inside the coil. The voltage
generated in the sensor may be detected by an external means
connected to the sensor. The voltage can be interpreted as the
first fluid being replaced by the second fluid. Other sensor means
may of course be used.
When the second fluid is replaced by the third fluid, the second
float may sink to its second position. The first float may sink
with the second float, as it is the second float that is limiting
the extent to which the first float may sink. Thus, the relative
displacement between the first and the second float may be
maintained at this stage. Since the first float may sink further as
the second float sinks, the magnet also sinks. This movement of the
magnet relative to the coil again generates a voltage. This second
voltage can be interpreted as the second fluid being replaced by
the third fluid.
When the third fluid is replaced by the second fluid and the second
fluid is then replaced by the first fluid, the exact opposite
results may occur.
It should be understood that this arrangement will work just as
well when the first fluid is replaced directly by the third fluid,
and vice versa. If this occurs, one larger displacement would be
detected.
Take, as another example, the case where the second float has the
magnet attached to it, the third fluid is present and both the
first and second floats are in their second positions (e.g.
adjacent the second, upper opening of the passageway). When the
third fluid is replaced by the second fluid, the second float may
rise and the first float may remain in its second position. The
second float may be stopped in its first position by its
interaction with the first float. The displacement/motion of the
second float may be detected by the sensor. This may occur as the
magnet passes relative to the coil generating a voltage inside the
coil. The voltage generated in the sensor may be detected by an
external means connected to the sensor. The voltage can be
interpreted as the third fluid being replaced by the second fluid.
Other sensor means may of course be used.
When the second fluid is replaced by the first fluid, the first
float may rise to its first position. The second float may rise
with the first float, as it is the first float that is limiting the
extent to which the second float may rise. Thus, the relative
displacement between the first and the second float may be
maintained at this stage. Since the second float may rise further
as the first float rises, the magnet also rises. This movement of
the magnet relative to the coil again generates a voltage. This
voltage can be interpreted as the second fluid being replaced by
the first fluid.
When the first fluid is replaced by the second fluid and the second
fluid is then replaced by the third fluid, the exact opposite
results may occur.
It should be understood that the invention will work just as well
when the third fluid is replaced directly by the first fluid, and
vice versa. If this occurs, one larger displacement would be
detected.
The apparatus may comprise a sealing element. The sealing element
may be located between the second float and the first opening. The
sealing element may be located between the first float and the
second opening. The sealing element may be annular. The sealing
element may surround the first/second opening. The sealing element
may be attached to the first/second float. The sealing element may
be attached to the remainder of the apparatus (i.e. not to one of
the floats), e.g. the main body, preferably the end plate. The
sealing element may comprise a resilient material, e.g. rubber. The
sealing element may seal against the tube or the coil housing or
the subsea equipment-protection apparatus (see below) or the main
body (see below) or any other part of the apparatus (other than the
other float).
The apparatus may comprise a main body. The main body may contain
the passageway, the tube, the coil and/or the coil housing. The
main body may be in the form of an end plate. The main body may be
attached to the tube, the coil, the coil housing and/or the subsea
equipment-protection apparatus or subsea cap (see below). The main
body may be a socket that fits within a hole in the subsea
equipment-protection apparatus or subsea cap. The plate may be
proximate the first opening. The end plate may be proximate the
second opening. There may be an end plate proximate each opening.
The end plate may be planar. The end plate may be annular in shape.
The end plate may be substantially concentric with the rod(s), the
coil, the tube and/or the coil housing.
An embodiment of the invention may take the form of a subsea
equipment-protection apparatus or subsea cap, the subsea
equipment-protection apparatus or subsea cap comprising the fluid
monitoring apparatus as described above.
The subsea equipment-protection apparatus or subsea cap may
comprise a surface. The surface may comprise an opening in which
the fluid monitoring apparatus is located. The surface may be
unbroken in the vicinity of the opening. This may allow fluid to
collect in the vicinity of the fluid monitoring apparatus. By
"unbroken surface" it is meant that the surface of the cup is
substantially free of holes.
The subsea equipment-protection apparatus or subsea cap may be
convex. The fluid monitoring apparatus and the opening may be
located in an upper portion of the surface. Again, this may allow
fluid to collect in the vicinity of the fluid monitoring
apparatus.
The subsea equipment-protection apparatus may be the
subsea-protection apparatus described in UK patent application no.
1421016.5.
The subsea equipment-protection apparatus or subsea cap may have a
hollow convex top portion. It should be noted that as used herein
the reference to the top/upper parts and bottom/lower parts are
with reference to the orientation of the device when in use, where
the base will be closer to the sea-bed (or other underwater
surface) and the top will be further from the sea-bed. Similarly,
references to a vertical direction or horizontal direction are used
in a manner that is consistent with this, with the horizontal being
generally parallel with the sea-bed and the vertical extending
normal from the sea-bed.
The hollow convex top portion may be generally dome-shaped.
The subsea equipment-protection apparatus may be placed over subsea
equipment, such as a wellhead, to protect it and to gather possible
leaking hydrocarbons. The subsea cap may be placed over subsea
equipment to gather possible leaking hydrocarbons.
Leak-monitoring of subsea equipment is an important consideration.
In known subsea equipment-protection or cap systems, no such
leak-monitoring is provided. Instead, the leak-monitoring may be
provided integrally as part of the subsea-equipment itself. Due to
the presence of the subsea equipment-protection apparatus and the
location of the fluid monitoring apparatus, leaking hydrocarbons
may gather in an upper region of the subsea equipment-protection
apparatus or cap. These leaking hydrocarbons, which are typically
less dense than water, displace water from the upper region of the
cap and may be held in the upper region of the subsea
equipment-protection apparatus by the subsea equipment-protection
apparatus. In this regard the dome-shaped subsea
equipment-protection apparatus or cap is particularly
advantageous.
The subsea equipment-protection apparatus or cap may comprise a
hole in an upper portion of the subsea equipment-protection
apparatus, for example a circular hole. The hole may be provided at
the upper most position of the subsea equipment-protection
apparatus. The hole may be provided at a center of symmetry of the
subsea equipment-protection apparatus. The fluid monitoring
apparatus may be located in this hole.
The subsea equipment-protection apparatus or cap may comprise a
vent hole that is configured to allow small amounts of gas to vent.
The hole may be separate from the apparatus of the present
invention. Small amounts of gas may be given off from the sea bed
and/or subsea equipment. This may be vented through the small hole
to prevent the apparatus of the present invention from detecting
the small amount of gas, which would effectively be a false
positive for such small amounts of gas. The vent hole may be
proximate the fluid monitoring apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Certain preferred embodiments of the invention will now be
described by way of example only with reference to the following
drawings in which:
FIG. 1 shows a schematic view of an embodiment of a fluid
monitoring apparatus of the present invention when a first fluid is
present;
FIG. 2 shows another schematic view of the apparatus of FIG. 1 when
a second fluid is present; and
FIG. 3 shows another schematic view of the apparatus of FIG. 1 when
a third fluid is present.
DETAILED DESCRIPTION OF THE INVENTION
Regarding FIG. 1, a fluid monitoring apparatus 1 is shown. The
fluid monitoring apparatus comprising a first float 10 and a second
float 20. The first float 10 has a density less than that of sea
water but greater than that of crude oil. The second float 20 has a
density less than crude oil but greater than that of natural gas.
In FIG. 1, sea water is present in the vicinity of fluid monitoring
apparatus 1 so both the first float 10 and the second float 20 are
floating in their first positions, which are their upper most
positions in this embodiment.
The first float 10 comprises a rod portion 11 and a disc-shaped end
portion 12. The rod portion 11 and the end portion 12 are
concentric.
The diameter and thickness of the end portion 12 of the first float
10 is less than the diameter and thickness of the end portion 22 of
the second float 10.
The second float 20 comprises a rod portion 21 and a disc-shaped
end portion 22. The rod portion 21 and the end portion 22 are
concentric. The second float 20 comprises an internal bore sized
such that the rod portion 11 of the first float 10 can nest within
the second float 20.
The first float 10 nests within the second float 20 and they are
configured to slide relative to one another telescopically. The
rods 11, 21 are substantially concentric. Between the bore of the
second float 20 and the rod 11 of the first float 10 there are
stops (not shown) that limits the relative displacement of the
first float 10 and the second float 20.
The apparatus 1 comprises a passageway 30. The passageway has a
first opening 31 at a lower end and second opening 32 at an upper
end.
The rod 21 passes through the passageway from outside of the first
opening 31 to outside of the second opening 32. The end portion 20
is proximate the first opening 31. The second float 20 also
comprises a stopping member 23 attached to the opposite end of the
rod 21. The stopping member 23 is thus proximate the second opening
32. The stopping member 23 comprises openings for allowing fluid to
pass therethrough. The stopping member 23 has a diameter greater
than that of the passageway 30, thus preventing the second float 20
from being fully withdrawn from the passageway 30.
The end portion 12 of the first float 10 is located proximate the
first opening 31, but is located further from the first opening 31
than the end portion 22 is. The opposite end of the first float 10
is housed within the bore of the second float 20.
The passageway 30 is defined by a tube 33. The tube 33 has an
annular in cross section. Surrounding the tube 33 is a coil housing
34 that also has an annular cross section. The coil housing 34 is
made of plastic.
The tube 33 and the coil housing 34 are housed within a main body
35. The main body 35 comprises two end plates at opposite ends of
the passageway 30. The end plates are annular disks and connect to
the ends of the tube 33 and the coil housing 34. Further, when in
use, as shown in FIG. 1, the end plates connect to the subsea
equipment-protection apparatus 50 (only a portion of which is shown
in FIG. 1).
The fluid monitoring apparatus also comprises a sensor 40. The
sensor 40 comprises a permanent magnet 41 attached to the rod 11 of
the first float 10, and a metal coil 42 surrounding the permanent
magnet 41. The metal coil 42 is encapsulated within the coil
housing 34. The rod 11, the rod 21, the passageway 30, the tube 33,
the coil housing 34 and the end plates of the main body 35 are all
concentric and all have their longitudinal axes orientated in a
vertical direction. The metal coil 42 extends substantially over
the entire length of the passageway 30. The ends of the metal coil
42 are connected via connecting wires to a connector 43 to which a
cable may be connected for the signal generated in the sensor to be
relayed to a controller (e.g. on the sea surface) which may alert
the user to a change in fluid.
A protective cap 36 is located over the second opening 32 of the
passageway 30 and over the stopping member 33 of the second float
20. The protective cap 36 has openings (not shown) for allowing
fluid to pass therethrough. The protective cap allows the second
float 20 to move without being impeded.
Between the upper surface of the end portion 22 of the second float
20 and the main body 35 there is a sealing ring 37. The sealing
ring surrounds the first opening 31 of the passageway 30 and has a
diameter greater than that of the passageway 30 but less than that
of the end portion 22 of the second float 20.
Regarding FIG. 1, the apparatus 1 is shown in its configuration
when sea water is present. Since both the first float 10 and the
second float 20 have a density less than that of sea water, the
first float 10 and the second float 20 float to their first
positions. Thus, the upper surface of end portion 22 of second
float 20 engages the sealing ring 37 and the passageway 30 is
sealed such that no fluid can pass through the passageway 30. In
this situation the rod 11 of the first float 10 is full nested
within the bore of the second float 20 such that the upper surface
of the end portion 12 is adjacent the lower surface of the end
portion 22.
Regarding FIG. 2, the apparatus 1 is shown in its configuration
when oil is present. Since the first float 10 is denser than oil,
it has sunk to its second position. Since the second float 20 is
less than oil, it remains in its first position. The first float 10
is held in its second position by the buoyancy of the second float
20 by virtue of the stops. During the sinking of the first float
10, the permanent magnet 41 has passed relative to the coil 42,
thus generating a voltage. The voltage signal is relayed to the
connector 43 and then preferably on to a controller. The voltage
signal received at the connector 43 is indicative of only the first
float 10 sinking since the voltage signal is dependent on the
direction and distance of the displacement of the magnet. Thus, it
is possible to detect that the first float 10 only has sunk, and
hence that sea water has been replaced by oil.
Regarding FIG. 3, the apparatus 1 is shown in its configuration
when gas is present. Since the first float 10 and the second float
20 are less than dense than gas, they sink to their second
positions. It should be noted that the first and second positions
of the first float 10 are relative to the second float 20, and the
first and second positions of the second float 20 are relative to
the passageway. The displacement of the second float 20 is limited
by the stopping member 33 and the displacement of the first float
10 is limited by the stops. During the sinking of the second float
20, the first float 10 also sinks further, thus there is further
relative movement of the permanent magnet 41 and the coil 42
generating another voltage. The voltage signal is relayed to the
connector 43 and then preferably on to a controller. In the case
where oil is replaced by gas, the voltage signal received at the
connector 43 is indicative of the second float 20 sinking since the
voltage signal is dependent on the direction and distance of the
displacement of the magnet. Thus, it is possible to detect that the
second float 20 has sunk, and hence that oil has been replaced by
gas. In the case where sea water is replaced by gas, the voltage
signal is indicative of both the first float 10 and the second
float 20 sinking. Thus, it is possible to detect that both the
first and second floats have sunk, and hence that sea water has
been replaced by gas.
Of course, as can readily be appreciated, the system works in a
corresponding inverse fashion when gas is replaced by oil, or when
oil is replaced by sea water, or when gas is replaced by sea
water.
Further, it should readily be appreciated that the system may be
inverted such that the first and second floats are arranged to seal
the upper opening of the passageway. In such an embodiment, the
first float and second float would sink when gas is present, the
first float thus sealing the upper opening. The second float only
would float when oil is present, its displacement being limited by
the first float and the stops. The first float would remain sunk
when the oil is present and hence continue to seal the passageway.
The first and second floats would float when sea water is present,
thus opening the passageway. The displacement of the first float
would be limited by the stopping member. The magnet would be
attached to the second float.
* * * * *